1. Field of the Invention
The present invention relates to a resin-sealed type semiconductor device, and especially to a one-side resin-sealed type semiconductor device in which a surface of a lead frame on which a semiconductor element is mounted is sealed with a resin and a lead frame used therefor.
2. Description of Related Art
Resin-sealed type semiconductor devices each provided with a lead frame for electrically connecting electrodes of the semiconductor to an outer wiring and the like are widely used. In such a semiconductor device, a lead frame generally comprises a supporting portion for mounting a semiconductor element thereon, hanging lead portions for supporting the supporting portion, and lead terminal portions for connecting metal wires thereto. A lead frame used in the process of fabricating semiconductors includes a plurality of unit regions corresponding to a plurality of semiconductor devices so that the plurality of semiconductor devices can be fabricated at the same time. One unit region has a substantially rectangular shape. Each of the hanging lead portions extends inwardly from a corner portion of this rectangle, and in many cases, the lead terminal portions extend inwardly from side parts of the unit region.
FIG. 5 is an enlarged schematic pan view showing a part in the vicinity of a corner of a unit region.
In the central part of the substantially rectangular unit region (in the direction of arrow G), a supporting portion 51 is disposed. A hanging lead portion 52 extends from the supporting portion 51 toward the corner portion. In the side parts of the unit region, substantially rectangular lead terminal portions 53 are provided. Base end portions of the lead terminal portions 53 are connected to a peripheral frame part 50. The longitudinal direction of the hanging lead portion 52 and the longitudinal direction of the lead terminal portion 53 makes an angle of substantially 45xc2x0.
In a lead frame, a plurality of unit regions each having such a structure are arranged and connected to the frame part 50. In the process of fabricating semiconductor devices, a lead frame is sealed with a sealing resin in such a manner that the bottom surface of the lead terminal portion 53 is exposed. Thereafter, each unit of lead frame is cut along a cutting line M shown in broken line, and the cut end face is substantially in the same plane with the side surface of the sealing resin.
In order to obtain a small-sized semiconductor device, it is preferable that the length of the lead terminal portion 53 is as short as possible. However, since the lead terminal portion 53 functions as a lead for connection with outer wiring substrate, the lead terminal portion 53 needs to have a length (area) more than a predetermined length (area). From these reasons, the lead terminal portion 53 is formed to have a predetermined necessary minimum length L1.
The minimum distance between the hanging lead portion 53 and the lead terminal portion 53A adjacent to the hanging lead portion 53 must be large enough to ensure insulating reliability between them. However, in order to obtain a small-sized semiconductor device, it is preferable that the minimum distance between them is small. From these reasons, the minimum distance between them is designed to be a predetermined necessary minimum distance L2.
However, since the predetermined length L1 and the predetermine distance L2 are required to be secured, miniaturization of mounting area of a semiconductor device is limited.
An object of the present invention is to provide a semiconductor device in which each lead terminal portion has a length (area) necessary for outer connection and at has a length (area) necessary for outer connection and at the same time insulating reliability between the hanging lead portions and lead terminal portions is secured, and a lead frame used for the semiconductor device.
Another object of the present invention is to provide a semiconductor device having a small mounting area, and a lead frame used for the semiconductor device.
A semiconductor device according to the present invention comprises a semiconductor chip having electrodes on the surface thereof, a lead frame having a plurality of lead terminal portions for electric connection and a plurality of hanging lead portions each extending obliquely with respect to the lead terminal portions and supporting a supporting portion on which the semiconductor chip is mounted, metal wires for connecting the lead terminal portions and the electrodes of the semiconductor device, and a sealing resin for sealing the semiconductor element, the lead frame and the metal wires in such a manner that a part of each lead terminal portion is exposed. The plurality of lead terminal portions include chamfered lead terminal portions each having, at its head, a chamfered portion formed substantially in parallel with the hanging lead portion so as to avoid interference with the hanging lead portion.
Further, a lead frame according to the present invention comprises a plurality of lead terminal portions for electric connection and a plurality of hanging lead portions each extending obliquely with respect to the lead terminal portions and supporting a supporting portion on which the semiconductor chip is mounted. The plurality of lead terminal portions include chamfered lead terminal portions each having, at its head, a chamfered portion formed substantially in parallel with the hanging lead portion so as to avoid interference with the hanging lead portion.
According to this invention, the lead terminal portions are chamfered substantially in parallel with the hanging lead portion so as to avoid interference with the hanging lead portions. Accordingly, even if the chamfered lead terminal portion is disposed nearer to the hanging lead portion in comparison with the case of the conventional lead terminal portion, a distance more than a predetermined distance can still be secured between the lead terminal portion and the hanging lead portion.
That is, in a conventional lead frame, a lead terminal portion has a corner portion protruding toward a hanging lead portion. Therefore, it has been necessary to dispose the lead terminal portion substantially on the peripheral part side in order to avoid interference between an edge of the corner portion and the hanging lead portion and secure a distance more than a predetermined value therebetween. As a result, a unit region in a lead frame corresponding to a semiconductor becomes large, and the size in the plane direction of a semiconductor device using this unit region becomes large.
On the contrary, according to the present invention, the lead terminal portion has a chamfered portion at its head and is opposed to the hanging lead portion at this chamfered portion. Therefore, the hanging lead portion can be disposed at a more inner portion in comparison with the case of the conventional structure. Accordingly, a unit region of lead frame can be small-sized. As a result, the size in the plane direction of a semiconductor device can be reduced and the mounting area of the same can be also reduced.
The chamfered portion is preferably comprises a linear side (C chamfering side) in parallel with the lateral side of the hanging lead portion. However, other shapes are similarly effective as long as the portion is chamfered so as to avoid interference by the hanging lead portion. For example, the chamfered portion may comprise a curved side (for example, R chamfering side). Further, in the chamfered portion, the oblique side may extend through only a part or the whole width of the lead terminal portion.
It is preferable that the abovementioned chamfered lead terminal portion is disposed adjacent to the hanging lead portion.
Not only the lead terminal portion adjacent to the hanging lead portion but also another lead terminal portion adjacent to this chamfered lead terminal portion may be a chamfered lead terminal portion. However, in this case, the chamfered lead terminal portion adjacent to the hanging lead portion becomes shorter than the other chamfered lead terminal portions. Therefore, it is preferable that only lead terminal portions adjacent to the hanging lead portion have such a chamfered portion. In this case, there is no remarkably short lead terminal portion. Therefore, in a semiconductor device using such a lead frame, all the lead terminal portions can be suitably connected to metal wires and an outer wiring substrate.
When only each lead terminal portion adjacent to the hanging lead portion comprises a chamfered lead terminal portion, the chamfered portion preferably has an oblique side extending throughout the whole width of the lead terminal portion. Thereby a unit region of lead frame can be minimized and the size of a semiconductor device using the same can be minimized in plan view.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.